My long-term goal is to understand the regulation of airway epithelial mucus synthesis and secretion. We have developed and are in the process of characterizing a hamster primary tracheal epithelial (TE) cell culture system which is highly enriched in epithelial secretory cells. The TE cell culture system has the advantage of providing a single mucous secretory cell type uncontaminated by submucosal gland derived secretory cells. With this system, which I have shown produces high molecular weight mucous glycoproteins or mucins, I plan to study pathways and mechanisms of epithelial mucin secretion. I will focus on the possibility, suggested by our preliminary studies, that there are two types of mucin secretion in airway epithelial secretory cells; a form of constitutive or non-granule secretion and a form of regulated or granule secretion. I will use two clinically important classes of secretory agents to explore the granule and non-granule secretory pathways: proteases, represented by human neutrophil elastase (HNE); and irritants, represented by mustard oil. Initial studies will deal with defining secretion mechanisms in the TE cell culture system by describing the acute effects of HNE and mustard oil. Subsequent studies, which depend on maintaining TE cells in culture for more prolonged times than are now possible, will deal with the consequences of chronic stimulation of the individual secretory pathways. The experiments planned should provide sufficient information to pose subsequent questions about the biochemical mechanisms involved in constitutive and regulated secretion in these cells and the developmental induction of regulated secretion. It is hoped that definition of pathways and mechanisms of mucin secretion will provide insight into the pathophysiology of airway secretory cell hyperplasia.